Heated feeder system for diecasting apparatus

ABSTRACT

The present invention relates to a heated feeder system for feeding molten plastic material through a die to one or more mold cavities therein, including a heated feeder device in the nature of a screw comprising a rod having one or more spiral feeder passages formed on the outer surface thereof.

United States Patent Von Holdt 1 Feb. '15, 1972 [54] HEATED FEEDERSYSTEM FOR 2,075,476 3/1937 DIECASTING APPARATUS 3,091,812 6/19633,055,055 9/1962 [72] Inventor: John W. Von Holdt, 7430 N. Croname3,259,682 7/1966 Road, "1198, 60643 2,309,943 2/1943 Ernst ..l8/30 m3 '1d: A .29,1970 [22] 6 pr Primary Examiner-H. A. Kllby, Jr. [21] Appl- N-Z 32,91 Attorney-Gary, Parker, Juettner, Pigott & Cullinan 52 us. Cl..425/447 [57] ABSTRACT [51] Int. Cl. The present invention relates to aheated feeder system for [58] Field of Search ..l8/ 12 SM, 12 SN, 30 SM,30 SP, feeding molten plastic material through a die to one or more18/30 SO, 30 SR, 30 SS, 30 RM, 30 RC, 30 RH, 30 mold cavities therein,including a heated feeder device in the RP, 30 RV, 30 PM, 30 PP, 30 PT,30 OT nature of a screw comprising a rod having one or more spiralfeeder passages formed on the outer surface thereof. [56] ReferencesCited a 11 Claims, 17 Drawing Figures UNITED STATES PATENTS 2,359,83910/1944 Goessling .Q ..18/30 SP UX PATENFEDFEB 1 5 I972 3,642, 11 8SHEET 1 [IF 4 I ZEFJ 20 12 7% yam 016m HEATED'FEEDER SYSTEM-FORDIECASTING APPARATUS BRIEF SUMMARY OF THE INVENTION In the use ofdiecasting to manufacture plastic parts, it is sometimes useful to heatthe metal die in order to'maintain the plastic material in a moltenconditionuntil it reaches the die cavity, and it is known in the art touse heating electrode members for this purpose. In accordance with:knownpractice, one or more heating electrode members are inserted in boresprovided therefor inthe metal die, thereby heating the die including thepassageways through'which the molten'plastic material flows in order topass through the die to the mold cavity therein. In other words, theknown practice is to heat substantially the entire die, which of courseautomatically serves to heat the plastic material as it flows throughthe die to the die cavity.

It is a general object of the present invention to-provide an improvedfeeder system for a die which serves to heat the passages through whichthe plastic material flows to reach the die cavity without heating theentire body of the die.

Another of my objects is to provide a feeder system as lastabove-mentioned which can if desired be utilized to heat substantiallythe entire length of the passageways for the plastic material from thenozzle where the plastic enters the die to the cavity where the plastichardens to form a desired part.

A further object of the invention is to provide a heated feeder memberin the nature of a screw comprising a-rod having a helical sprue orfeeder passage formed on the outside thereof and heating means containedwithin the rod.

Relative to the foregoing objective, it will be understood that in thediecasting of plastic it is necessary to maintain the plastic materialwithin a predetermined temperature range so that the plastic is heatedabove its melting point but not above the temperature at whichdegradation begins to occur. The foregoing range will of course varywith different types of plastic material. However, by way of example, aplastic material may have a melting temperature of 275 F., and maybecome subject to degradation at a temperature of 375 F., in which casethe temperature of the plastic while it is in the die should always bemaintained in the foregoing range.

Thus, if the plastic material is allowed to be in the die for too long atime it will become overheated and subject to degradation, and it istherefore desirable once plastic material is fed into the die that itshould be used with a predetermined time. For example, in certainapplications it is considered desirable that the mold not contain moreplastic material than will be utilized in the die cavity in threemolding cycles, i.e., once plastic material enters the inlet to the moldit should be supplied to the die cavity and utilized within threemolding operations. However, as indicated above the problem ofdegradation is much more critical with some plastic materials than withothers, and consideration should be given to the particular plasticmaterials to be used when formulating the design of the die.

In accordance with the objective stated hereinabove, I provide a heatedfeeder screw member to control the flow of plastic material through thedie to the mold cavity. That is, I provide a rod having one or morehelical passages or sprues formed externally thereon, and I heat the rodby any suitable means, as for example by a heating electrode containedwithin the rod. With such an arrangement it is possible to vary thepitch of the helical passage, the depth of the passage and the diameterof the screw in order to control the amount of plastic material withinthe helical passageways and the time during which the plastic materialis in effect stored or in melt within the die before being utilized inthe mold cavity during a molding operation. In addition, it is possibleto provide a screw having a plurality of sprues in the form ofindependent helical passageways formed thereon so that a single screwmember may be utilized to supply plastic material to a plurality ofdifferent mold cavities.

The foregoing and other objects and advantages of my invention will beapparent from the following description thereof, taken in conjunction.with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of die castingapparatus having a feeder or runner system constructedin accordance withthe present'invention, the embodiment shown comprising a single feedscrew member for feeding two mold cavities;

FIG. 2 Ba fragmentary sectional view taken substantially along the line2-2 of FIG. 1; 1

FIG. 3 Ba sectionalview showing a modified form of the in ventionwherein a sleeve'member is mounted in a bore formed in'a manifold blockand a heated feed screw is located within the sleeve;

FIG. 4 isa sectional view taken substantially along the line 4-4 of FIG.3;

FIG. 5 is a sectional view taken substantially along the line 55 of FIG.3; i

FIG. 6 is a fragmentary elevational view of the feed screw of FIG. 3illustrating how plastic material supplied by a nozzle to the center ofthe screw is divided and fed in two opposite directions toward therespective end portions of the screw;

FIG. 7 is a sectional view illustrating the mounting of a feed screwmember in a bore formed in a solid manifold block of a die, the feedscrew being arranged for feeding plastic material from a common inlet toa pair of mold cavities;

FIG. 8 showsa modified form of the invention where four feed screwmembers are arranged to intersect at a common inlet point and serve tofeed plastic material from the inlet to four different mold cavities;

FIG. 9 is a sectional view taken substantially along the line 9-9 ofFIG. 8;

FIG. 10 is an elevational view, partly in section, showing a modifiedform of feed screw in accordance with the present invention wherein thescrew is provided with two independent sprues in the form of two leadthreads formed on the screw;

FIG. 11 is a sectional view taken substantially along the line llllofFIG. 10;

FIG. 12 is a sectional view taken substantially alongthe line 1212ofFlG. I0; I

FIG. 13 is a schematic view illustrating an Hshaped arrangement of onescrew with a single lead thread and two screws with double lead threadsutilized to supply plastic material from a common inlet to eightseparate mold cavities;

FIG. 14 is an elevational view, partly in section, showing a modifiedform of feed screw in accordance with the invention wherein the screw isprovided with four independent spruesin the form of four lead threadsformed on the screw; I

FIG. 15 is a sectional view taken substantially along the lin 15-15ofFIG.14;

FIG. 16 is a sectional view taken substantially along the line 16-16ofFlG. l4; and

FIG. 17 is a schematic view showing the manner in which the multiplelead screw of FIG. 14 may be utilized to feed eight different moldcavities from a common inlet located adjacent the midportion of thescrew.

Now, in order to acquaint those skilled in the art with the manner ofmaking and using my invention, I shall describe, in conjunction with theaccompanying drawings, certain preferred embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings,FIG. 1 shows a die assembly including an inlet 20 for molten plasticmaterial and a pair of vertical feeder openings 22 and 24 whichcommunicate with corresponding mold cavities 26 and 28. The upperportion of the die includes a pair of parallel spaced-apart platemembers 30 and 32 which are removably connected to one another and whichtogether with side plate members 34 and 36 (see FIG. 2) define agenerally rectangular space for a manifold assembly 38. The manifoldassembly 38 includes upper and lower manifold plates 40 and 42 whichdefine therebetween a horizontal bore within which is mounted a feedscrew 44 constructed in accordance with the present invention. Themanifold plates 40 and 42 are removably connected together by cap screws46 and 48 as shown in FIG. 2. The feeder screw 44 has a longitudinalbore 50 formed therein to accommodate heating means for heating thescrew member, and in the embodiment shown in FIG. 1 a heating electrode52 is positioned within the bore 50. However, it will be understood thatvarious other heating means may be utilized, e.g., hot oil or water maybe conducted through the bore 50 to heat the screw.

In the embodiment shown in FIG. 1, the screw 44 has a single leadhelical thread or sprue 54 formed on the exterior thereof which extendsfor substantially the entire length of the e screw and whichcommunicates at-the respective ends of the screw with the verticalpassages 22 and 24 leading to the die cavities 26 and 28. Adjacent themidportion of the screw 44, the upper manifold plate 40 is provided witha passage 56 which communicates with the inlet 20.

It will be understood from the foregoing that molten plastic materialsupplied to the inlet will be fed into the helical groove 54 and dividedfor delivery toward the opposite ends of the screw 44 and ultimatelythrough the vertical passages 22 and 24 to the die cavities 26 and 28.The heating electrode member 52 will heat the screw 44 and maintain theplastic material in molten condition as it flows along the screw to thevertical feeder passages. With such an arrangement, the heating of theplastic material is accomplished without heating major portions of thedie as is common in conventional heated die assemblies.

It is important to understand that the helical groove 54 formed in thescrew 44 comprises an extremely advantageous arrangement because itaffords a broad range of variables for control over the amount ofplastic material which is contained in the screw and the time intervalduring which such material is stored in the screw before being conductedto the mold cavities for a molding operation. Thus, the pitch of thehelical groove, the depth of the groove and the diameter of the screw 44can each be designed to provide optimum results in a givenapplication'depending upon the weight and thickness of the piece part,the cycle time, thenumber of mold cavities and the distance from theinlet nozzle to the mold cavities. Such an improved runner systemeliminates conventional three plate runner systems, hot runner platesand leaking of plastic out of runner systems as often occurs when theentire mold is heated. The foregoing improved runner system alsominimizes startup time since it is not necessary to heat up majorportions of the mold, and it permits a reduction in the molding cycletime so as to greatly improve automatic molding operations.

FIGS. 3-5 show a portion of a die assembly including an inlet 58 and apair of vertical feeder openings 60 and 62 which communicate withrespective mold cavities 64 and 66. The upper portion of the die block67 has a horizontal bore 68 formed therein in which is mounted amanifold assembly 70. A steel sleeve 72 is mounted in the bore 68, and afeeder screw 74 is positioned within the sleeve, the screw having anexternal helical groove or sprue 76 formed therein and an internalheating electrode 78, substantially as in the embodiment of FIG. 1. Apair of threaded end plugs 80 and 82 maintain the screw 74 within thesleeve 72. It will be noted that the sleeve 72 is relieved on itsexternal surface so as to reduce the area of contact between the sleeveand die block 67. In the embodiment shown, such relief is provided byforming a plurality of annular grooves 84 in the outer surface of thesleeve. It will be understood that the several annular grooves 84 neednot communicate with one another since they do not serve as passagewaysfor the plastic material.

The sleeve 72 described hereinabove serves the purpose of keeping themolten plastic material from directly engaging the die block 67, therebymaintaining the block in clean condition and minimizing damage thereto.The sleeve also tends to serve as an insulator so as to minimizeconduction of heat to the block 67 FIG. 7 illustrates a solid manifoldarrangement where a horizontal bore 86 is formed in a solid manifoldblock 88 and a feeder screw 90 is disposed within the bore and isprovided with an external helical lead thread or sprue 92 which feedsplastic material from a common inlet 94 in the block 88 to a pair ofvertical passages 96 and 98 leading to corresponding die cavities 100and 102. As in the other embodiments. heating means such as a heatingelectrode 104 is provided within an internal bore formed in the screwfeeder member. In many applications a solid manifold of the foregoingtype will provide greater strength characteristics than a split manifolddesign.

FIGS. 8 and 9 illustrate the use of four feeder screws in combination tofeed plastic material to four different mold cavities. The feeder screwsI06, 108, I10 and 112 are arranged along two perpendicular axes so as tointersect at a common point. By locating a main inlet 113 at the pointof intersection, it will be understood that plastic material may besupplied along the four screws to corresponding -,vertical passageways114, 116, 118 and. 120 leading to respective mold cavities. Theforegoing screws are each of the type having a single lead, and in eachinstance the spiral passage or sprue communicates with a correspondingone of the vertical passages. In the particular embodiment shown, eachof the vertical passages has a conventional heater probe located thereinas shown at 122, 124, 126 and 128, such heater probes being of adiameter significantlyless than the corresponding passages so as toallow space for the plastic material to flow around the outside of theheater probes to the respective mold cavities, one such cavity beingshown at 130 in FIG. 9.

FIGS. 10-12 show a modified form of feeder screw 132 having two leads134 and 136 which join at the midportion of the screw as shown at 138.Such a multiple sprue feeder screw can of course be utilized to feed anincreased number of die cavities from a common inlet. For example, FIG.13 illustrates schematically the manner in which three of the doublelead feeder screws 132 may be combined in an I-I-sh'aped arrangement forfeeding plastic material from a common inlet 140 to eight differentvertical passages 142, 144, 146, 148, 150, 152, 154 and 156 which leadto corresponding mold cavities.

'FIGS. 14-16 show still another modified form of feed screw 158constructed in accordance with the present invention.

. material from the common inlet 168 to eight different verticalpassages170, 172, 174, 176, 178, 180, 182 and 184 which lead tocorresponding mold cavities.

While I have described my invention in certain preferred forms,modifications within the scope of my invention will readily occur tothose skilled in the art, particularly with my disclosure before them.In particular, the term heating means should be interpreted broadlyenough to include cooling means in any application where a thermosettingmaterial is being used rather than a thermoplastic material is beingused rather than a thermoplastic material for the reason that while theinvention has been described primarily in connection with the molding ofthermoplastic materials it may also be used to advantage in the moldingof thermosetting materials. The term diecasting as used herein isintended to be synonymous with the terms mold or plastic mold and refersto a mold assembly for molding plastic parts.

I claim:

1. In a mold assembly for molding plastic parts, said assembly being ofthe type having an inlet for molten plastic material or the like and atleast one mold cavity to which such molten material is conducted fora'molding operation, an improved feeder system comprising incombination, manifold block means disposed within the mold assembly andhaving an elongated recess therein which communicates with an inletpassage for receiving molten plastic material and also communicates witha mold cavity, feeder means positioned within said elongated recess,said feeder means comprising a sta-.

tionary rod member having at least one external helical groove formedalong the length thereof, said helical groove together with asurrounding wall of said elongated recess serving to define a helicalpassage for conducting molten plastic material from said inlet towardsaid mold cavity, said rod member having an internal aperture extendingalong the length thereof, and heating means disposed within saidinternal aperture for heating said rod member thereby heating plasticmaterial which is conducted through said helical passage.

2. A feeder system as in claim 1 where said feeder means is disposedhorizontally and where one end of said feeder means communicates with agenerally vertical passage leading to said mold cavity.

3. A feeder system as in claim 1 where said feeder means is disposedhorizontally with its midportion positioned to receive plastic materialfrom an inlet passage and with each end of said feeder means incommunication with a respective generally vertical passage leading to acorresponding mold cavity.

4. A feeder system as in claim 1 where said heating means comprises anelectrical resistance unit disposed within a longitudinal bore formed insaid feeder means.

5. A feeder system as in claim 1 where a plurality of independenthelical grooves are formed in a single feeder means and arranged incommunication with a common inlet passage for feeding plastic materialto a plurality of corresponding mold cavities.

6. A feeder system as in claim 1 where said helical groove isapproximately semicircular in its cross-sectional configuratron.

7. A feeder system as in claim 1 where a tubular sleeve is disposed insaid elongated recess and said feeder means is disposed in saidelongated recess and said feeder means is disposed within said tubularsleeve.

8. A feeder system as in claim 7 where said tubular sleeve is relievedover a portion of its exterior surface to reduce surface area contactbetween said sleeve and said manifold block means.

9. A feeder system as in claim 1 here a plurality of said feeder meansare arranged in intersecting relation with the point of intersectionthereof located in communication with a common inlet passage.

10. In a mold assembly for molding plastic parts, said assembly being ofthe type having an inlet for molten plastic material or the like and atleast one mold cavity to which such molten material is conducted for amolding operation, an improved feeder'system comprising, in combination.manifold block means disposed within the mold assembly and having anelongated recess therein which recess is circular in cross-sectionalconfiguration and communicates with an inlet passage for receivingmolten plastic material and also communicates with a mold cavity, feedermeans positioned in close fitting relationship in said elongated recess,said feeder means comprising a stationary rod member having at least oneexternal helical groove formed along the length thereof, said helicalgroove together with a surrounding wall of said elongated recess servingto define a helical passage for conducting molten plastic material fromsaid inlet toward mold cavity, a longitudinal bore formed in said rodmember, and heating means located in said longitudinal bore for heatingsaid rod member thereby heating plastic material which is conductedthrough said helical passage.

. 11. A feeder system as in claim 10 where said feeder means is disposedhorizontally with at least one end of said feeder means in communicationwith a vertical passage leading to a corresponding mold cavity, andwhere said heating means comprises an electrical resistance unitdisposed within said longitudinal bore.

1. In a mold assembly for molding plastic parts, said assembly being ofthe type having an inlet for molten plastic material or the like and atleast one mold cavity to which such molten material is conducted for amolding operation, an improved feeder system comprising in combination,manifold block means disposed within the mold assembly and having anelongated recess therein which communicates with an inlet passage forreceiving molten plastic material and also communicates with a moldcavity, feeder means positioned within said elongated recess, saidfeeder means comprising a stationary rod member having at least oneexternal helical groove formed along the length thereof, said helicalgroove together with a surrounding wall of said elongated recess servingto define a helical passage for conducting molten plastic material fromsaid inlet toward said mold cavity, said rod member having an internalaperture extending along the length thereof, and heating means disposedwithin said internal aperture for heating said rod member therebyheating plastic material which is conducted through said helicalpassage.
 2. A feeder system as in claim 1 where said feeder means isdisposed horizontally and where one end of said feeder meanscommunicates with a generally vertical passage leading to said moldcavity.
 3. A feeder system as in claim 1 where said feeder means isdisposed horizontally with its midportion positioned to receive plasticmaterial from an inlet passage and with each end of said feeder means incommunication with a respective generally vertical passage leading to acorresponding mold cavity.
 4. A feeder system as in claim 1 where saidheating means comprises an electrical resistance unit disposed within alongitudinal bore formed in said feeder means.
 5. A feeder system as inclaim 1 where a plurality of independent helical grooves are formed in asingle feeder means and arranged in communication with a common inletpassage for feeding plastic material to a plurality of correspondingmold cavities.
 6. A feeder system as in claim 1 where said helicalgroove is approximately semicircular in its cross-sectionalconfiguration.
 7. A feeder system as in claim 1 where a tubular sleeveis disposed in said elongated recess and said feeder means is disposedin said elongated recess and said feeder means is disposed within saidtubular sleeve.
 8. A feeder system as in claim 7 where said tubularsleeve is relieved over a portion of its exterior surface to reducesurface area contact between said sleeve and said manifold block means.9. A feeder system as in claim 1 here a plurality of said feeder meansare arranged in intersecting relation with the point of intersectionthereof located in communication with a common inlet passage.
 10. In amold assembly for molding plastic parts, said assembly being of the typehaving an inlet for molten plastic material or the like and at least onemold cavity to which such molten material is conducted for a moldingoperation, an improved feeder system compriSing, in combination,manifold block means disposed within the mold assembly and having anelongated recess therein which recess is circular in cross-sectionalconfiguration and communicates with an inlet passage for receivingmolten plastic material and also communicates with a mold cavity, feedermeans positioned in close fitting relationship in said elongated recess,said feeder means comprising a stationary rod member having at least oneexternal helical groove formed along the length thereof, said helicalgroove together with a surrounding wall of said elongated recess servingto define a helical passage for conducting molten plastic material fromsaid inlet toward mold cavity, a longitudinal bore formed in said rodmember, and heating means located in said longitudinal bore for heatingsaid rod member thereby heating plastic material which is conductedthrough said helical passage.
 11. A feeder system as in claim 10 wheresaid feeder means is disposed horizontally with at least one end of saidfeeder means in communication with a vertical passage leading to acorresponding mold cavity, and where said heating means comprises anelectrical resistance unit disposed within said longitudinal bore.